Technical Field
The present invention relates to a sheet manufacturing apparatus and a sheet manufacturing method.
Related Art
Conventionally, fibrous materials are deposited and coupling forces act between the deposited fibers to obtain a sheet-like or film-like molded body. A representative example is the manufacture of paper by paper forming that uses water. Currently, paper forming is widely used as a method for manufacturing paper. Generally, paper manufactured by paper forming has a structure in which cellulose fibers originating from, for example, wood materials are entangled and are partially bonded by bonding forces such as hydrogen bonds.
However, paper forming is a wet type process requiring large quantities of water. In addition, after the paper has been formed, the need arises for dehydration and drying; therefore, the energy and time consumed become extremely large. Furthermore, the water used must be appropriately treated as wastewater. The apparatus used in paper forming often require large-scale utilities and infrastructure for water, power, and wastewater facilities, and is difficult to reduce in size.
Thus, from the perspective of saving energy and protecting the environment, methods that use almost no water, referred to as dry type methods, are anticipated as paper manufacturing methods that will replace paper forming. For example, Japanese Laid-Open Patent Application No. 2012-144819 discloses a paper recycling apparatus that defibrates and deinks the paper that becomes the raw material, adds a small amount of moisture, and forms the paper in a dry type process.
The performance demanded from sheets, such as paper, is mechanical strength, for example, tensile strength and tear resistance. In the technology described in Japanese Laid-Open Patent Application No. 2012-144819, the water moisture added during the formation of paper is believed to act to elicit hydrogen bonds originating in hydrogen groups as the bonding force between the fibers forming the paper. However, after the paper has been formed, the hydrogen bonds will have reduced bonding force in the presence of water. Therefore, in paper in which hydrogen bonding is used as the coupling force between the fibers, inadequate mechanical strength and shape deformation arise when the paper is placed in a high-humidity environment or is dampened by water. Consequently, binding a plurality of fibers with resin was considered. However, mechanical strength was inadequate at times even when bonded by resin. The cause was the lower moisture content contained in the fibers when the sheet was formed. One cause of the lower moisture content contained in the fibers was the loss of moisture during defibration in a dry type process when paper having relatively low moisture content was the raw material. Another cause was the lower moisture content originally included in the paper that became raw materials. This occurs when the manufacturing apparatus was installed in a low-humidity environment, and when the paper raw materials were placed in a low-humidity environment.